Studies are being carried out on primary cultures of rat brain astrocytes which have been transformed with Herpesvirus, and on cell lines derived from human astrocytomas, types II, III, and IV. The levels of key metabolites, glucose, glycogen, lactate, pyruvate, ATP, P-creatine, GABA, glutamate, glutamine and cyclic nucleotides were measured various times after refeeding confluent cultures with Eagle's Minimal Essential Medium containing glucose. Gylcogenolyis in the rodent cell line is regulated by the availability of glucose, or by catecholamine induced increases in cyclic AMP. Alterations in the energy status also are correlated with glycogenolysis. The rate of anaerobic and aerobic glycolysis was examined in the human cell lines. Over 50% of the total glucose consumed appears in the medium as lactate and pyruvate. The amino acids glutamate and glutamine are rapidly taken up and may constitute a quantitatively significant oxidizable carbon source. Glycogen levels are not affected by glucose administration (refeeding), and three of four times tested showed a catecholamine-induced glycogenolysis.